Circuit breaker operating mechanism



y 10, 1956 J. A. FAVRE 2,754,387

CIRCUIT BREAKER OPERATING MECHANISM Filed April 30, 1954 3 Sheets-Sheet1 f Inventor:

E His torneg.

July 10, 1956 J. A. FAVRE CIRCUIT BREAKER OPERATING MECHANISM 3Sheets-Sheet 2 Filed April 50, 1954 FUZLY OPE/V FULL) 640550 FULLY OPE/VInventor:

John A. Fa e, bg W fl His tonnes.

y 10, 1956 J. A. FAVRE CIRCUIT BREAKER OPERATXNG MECHANISM 3Sheets-Sheet 3 Filed April 30, 1954 Inventor":

LDC/(007' DEV/CE Jo? A. Fag/2e, b5 7 H is A orn e3.

United States Patent CIRCUIT BREAKER OPERATING MECHANISM John A. Favre,Broomall, Pa., assignor to General Electric Company, a corporation ofNew York Application April 30, 1954, Serial No. 426,662

21 Claims. (Cl. 200-82) This invention relates to an operating mechanismfor circuit breaker, and more particularly to a mechanically trip-freeoperating mechanism which is capable of producing high speed reclosureof the circuit breaker upon opening thereof.

An important requirement for most circuit breakers is that the circuitbreaker contacts should be capable of tripping, or moving toward openposition, even while a thrust is being applied by the closing device ofthe breaker. To meet this requirement, it is conventional to provide thecircuit breaker with a mechanically trip-free operating mechanism. Themechanically trip-free mechanism usually comprises a collapsible linkagewhich is maintained in thrust-transmitting relationship by a trip-freelatch. If the closing device drives the mechanism in a direction toclose the contacts of the circuit breaker while a fault is present onthe line, the latch will be tripped at or near the end of the closingstroke, and as a' result, the mechanism will be rendered incapable oftransmitting continued thrust from the closing device to the contacts.Accordingly, the usual springs, which normally urge the contacts towardopen position, will then immediately become effective to collapse themechanism, to uncouple it from the closing device, and to open thecontacts. Such a conventional trip-free switch closing mechanism isdescribed in U. S. Patent 1,827,626 issued to Carl Thumin and assignedto the assignee of the present invention.

Before the usual mechanically trip-free mechanism can be reclosed, it isnecessary that the operating linkage and the trip-free latch be reset,and it is further necessary that the closing device be returned at leastpartially to its original retracted position. Only after this resettingand retraction has occurred, are the usual linkage and closing deviceagain in a condition to transmit closing thrust to the contacts. Inprior mechanically trip-free circuit breakers this resetting of thelinkage and retraction of the closing device has required an appreciableperiod of time. This period of time is highly undesirable where rapidreclosing of the circuit breaker is necessary in order to maintaincontinuity of service on the circuit.

To shorten the delay required for complete resetting of the circuitbreaker mechanism and closing device, certain prior arrangements havebeen devised, but these arrangements have often been rather complex andcostly. For example, it is common in a pneumatically-operated circuitbreaker to provide a dump valve for quickly evacuating the pressurizedair beneath the circuit breaker closing-piston in order to permit rapidreversal or retraction of the piston without undue impedence from theresidual pressurized air. In such arrangements only when the piston isretracted, may the circuit breaker then be reclosed. An example of suchan arrangement is shown and claimed in U. S. Patent 2,479,315 issued toTR Coggeshall and assigned to the assignee of this application. Sincethe required dump valves are rather "ice costly, it obviously would bedesirable if rapid reclosing could be achieved without the need for dumpvalves.

Other attempts have been made to shorten the delay required forresetting by providing a mechanism which utilizes a pair of latches, onea non-trip-free latch and the other a trip-free latch. An example ofsuch a mechanism is shown in U. S. Patent 2,282,348, issued to CarlThumin and assigned to the assignee of the present invention. In such amechanism the presence of more than one latch requires that complexmeans must be utilized for transferring control from one latch to theother.

Accordingly, it is an object of my invention to pro vide a new andimproved mechanically trip-free operating mechanism which requires onlya single latch in order to provide for rapid reclosing.

It is a further object of my invention to provide a mechanicallytrip-free linkage which may be driven toward closed position by aclosing device which requires no subsequent retraction prior to againreclosing the linkage after a subsequent tripping. This feature permitsa rapidly-reclosing, pneumatically-operated circuit breaker to beconstructed without dump valves since a return of the operating pistonback to its initial position is no longer a necessary pre-requisite to asubsequent closing operation.

A further object of my invention is to construct the mechanicallytrip-free mechanism in such a manner that the closing device remainscoupled to the mechanism at all times, even during a trip-freeoperation. Hence, as soon as the trip-free latch is reset, the closingdevice is prepared to drive the circuit breaker toward its reclosedposition.

A further object is to construct the mechanism in such a manner that theapplication of reclosing power to the tripped mechanism prior to fulllatch-resetting is effective to accelerate the latch resetting actionand thereby reduce the reclosing time to a minimum.

In accordance with one form of my invention, the circuit breakercomprises a movable switch member and a collapsible toggle coupled tosaid switch member. The toggle has a knee movable toward toggle centeron one side of said center to close said switch member and movable awayfrom toggle center on the other side thereof to open the switch member.For moving the knee toward toggle center on one side thereof whereby toclose the switch member, there is provided a source of motive powerhaving a driving member coupled to the knee. Cooperating with thetoggle, there is provided trip-free latch means which may be tripped torender the toggle ineffective to drive or hold the switch member closed.Normally ineffective toggle-collapsing means is rendered effective bytripping of the latch means to move the knee away from toggle center onsaid other side of said center whereby to effect opening movement of theswitch member. The latch means has a pair of dilferent latched positionsin which it is effective to maintain the toggle operative to transmitclosing thrust to the switch member. When the circuit breaker is trippedby moving the latch means out of one of its latched positions, the latchmeans resets into its other latched position before the completion ofthe opening stroke by the circuit breaker. Reclosing power applied tothe toggle before the latch has completely reset is effective toaccelerate the latch resetting process. As soon as the latch resets,this reclosing power becomes effective to immediately reverse thethen-opening circuit breaker and to return it to its closed position.

My invention will be better understood from the following descriptionwhen considered with the accompanying sheets of drawings, and its scopewill be pointed out in the appended claims.

Referring to the drawings, .Fig. 1 is a partially schematic view of acircuit breaker having a fluid-motor actuated operating mechanismconstructed in accordance with the present invention. By the solid linesof Fig. 1 the breaker is shown in open position with the piston to thefluid motor in a lowered position. The dotted lines of Fig. 1 illustratean intermediate position through which the mechanism will move as thepiston is elevated toward its upper circuit breaker closed position.

Fig. 2, by solid lines, shows the circuit breaker of Fig. 1 in a fullyclosed position with the piston in its fully elevated position. Thedotted .lines illustrate an intermediate position through which themechanism would move after having been tripped from the solid lineposition of Fig. 2.

Fig. 3 illustrates the circuit breaker of Fig. V1 in open position withthe piston of the fluid motor in an elevated position.

Fig. 4 illustrates the circuit breaker of Fig, 1 in another elosedposition, but with its actuating piston in a lowered position.

Fig. 5 is ,a diagrammatic layout of a circuit breaker operating systemembodying the mechanism of Fig. 1.

Referring more specifically to Fig. 1, the circuit breaker embodying myinvention comprises a pair of relativelymovable contacts 1d, 11separable to interrupt the current flowing through power circuit 9.These contacts are biased toward open position by a compression spring12 acting through a reciprocable circuit breaker operating rod 13 ofinsulating material connected to contact 10. For moving the contacttoward closed position, I have provided a fluid motor 14 having areciprocable piston 15, which is coupled to the operating rod 13 bymeans of the mechanically trip-free operating mechanism generallyindicated at 16.

The operating mechanism 16 includes a primary toggle links 213 and 21which are pivotally joined by means of a pin forming a toggle knee 22.,For coupling the inner end of toggle link 21 to contact operating rod13, there is provided an output crank 23 supported on a fixed pivot 24.The arms of the crank are respectively pivotally joined to the togglelink 21 and the operating rod 13. For guiding and supporting the outerend of link 29, there is provided a carrier element 26, which ispivotally supported on a fixed pivot pin 27 and is pivotally joined totoggle link 2i) by a toggle support pin 25..

As will appear more clearly hereinafter, the carrier element 26 can belatched in either an upper .or a lower position. In Fig. 1 the carrierelement 26 is shown latched in its upper position. For carrying out thislatching function, there is provided a trip-free latch means including asecondary toggle 30 comprising a first link 31 pivotally supported on afixed pivot pin 32 and a second link 33 pivotally joined to the supportpin 25 of the primary toggle 16. Secondary toggle links 31 and 33 arepivotally joined to each other by a pin forming a knee 34 for thesecondary toggle. For latching the knee 34 in a predetermined fixedposition, there is provided a trip-free latch member 35 pivotallysupported on fixed pivot 36 and biased counterclockwise about this pivotinto the latching position shown in Fig. 1 by means of a resettingspring 37. For tripping, or unlatching, the latch member 35 in responseto predetermined electrical conditions, there is provided a trippingsolenoid 33, which when activated, moves latch member 35 clockwiseagainst the bias of resetting spring 37. As will appear hereinafter,especially from .Fig. ,5, this tripping solenoid 38 may be activated inresponse to a predetermined electrical condition in circuit 9. Theoperation of this electroresponsive latch structure is described ingreater detail hereinafter.

The fluid motor 14, which provides a source of motive power for closingthe breaker, has its piston coupled to toggle link by means of a pistonrod 40 and a connecting link 41 pivotally joined at .42 and 43 to thetoggle link 20 and the piston rod 40, respectively. The piston rod 40 isguided for linear movement by suitable guide rollers 44. For reasonswhich will soon be apparent, the fluid motor 14 is double-acting. Thatis, by selectively admitting pressurized fluid, preferably air, toeither side of the piston 15 by means of conduits 45 and 46, the pistonmay be selectively driven either upwardly or downwardly, depending uponits initial position in the cylinder of the motor.

A cycle of operation for the mechanism will now be described. Assume,first, that the circuit breaker is in the solid-line open position ofFig. 1 with the driving piston 15 in its lower position. So long as thetrip-free latch member 35 remains in its latched position, the togglesupporting pivot pin 25 remains fixed and the collapsible primary toggle20-22 is capable of transmitting closing thrust from the driving piston15 to the operating rod 13 of the circuit breaker. Assume, then, thatthe latch member 35 remains latched as the piston 15 .is driven upwardlyfrom its lowered position of Fig. 1, as indicated by arrow 47, To drivethe piston upwardly, pressurized fluid is admitted to the space beneathpiston 15 by means of conduit 46, as shown by the arrow 48 in Fig. 1..As the piston is driven upwardly, it moves the mechanism through thedotted-line, partially-closed, position of Fig. 1, and finally, when theupward stroke of the piston is completed, into the solid line,fully-closed, position shown in Fig. 2. It will be apparent that thisupward movement of the piston moves the knee 22 of the primary toggletoward the toggle center and into the substantially toggle-centerposition shown in Fig, 2, in which position the knee has encountered andis main tained by a pivotally-mounted prop member 50, which is biasedtoward a stable supporting position, underneath the knee by a suitablespring 51.

A circuit breaker opening, or tripping, operation will be now describedby referring to Figs. 2 and 3. When the tripping solenoid 38 isenergized to move the latch member 35 clockwise toward the dotted lineposition shown in Fig. 2, the knee 34 of the then-contracted secondarytoggle is immediately freed from the latch member 35 and is movedrapidly outward toward the dotted line position of Fig. 2 by the bias ofopening spring 12 discharging through the operating mechanism 16. As thesecondary toggle 34 extends toward its dotted line position, the togglesupporting pin 25 swings rapidly downward along an are 53 having itscenter at 27. This downward arcuate movement of the support pin causesthe primary toggle 20, 21 to collapse generally upwardly toward itsdotted line position of Fig. 2. Initiation of this upward collapsingmovement of the primary toggle is promoted by the fact that the prop 50and the pistonconnected linkage 40, 41 provide an upward force componentwhich acts through the knee 22 when the togglesupporting pin 25 movesarcuately downwardly. Obviously, this upward component of force actingthrough the toggle knee 22 buckles the toggle 20, 21 in an upwarddirection and causes toggle collapsing movement toward the dotted lineposition of Fig. 2. As the primary toggle 2t 21 continue in itscollapsing movement and as the toggle-supporting pin 25 continues in itsdownward arcuate movement the secondary toggle continues to extend, andas a result the knee 34 of the secondary toggle begins to return towardits latched position. This return movement of the knee 34 continuesuntil the link 31 engages a buffer or stop 55, as shown in Fig. 3. Whenthis engagement occurs the knee 36 has been returned to its originalposition, wherein it is latched by the latching member 35, which hasreset to its normal holding position of Fig. 3 under the bias of latchreset spring 37 This resetting of the latch member 35 is completed at anintermediate point in the contact opening stroke substantially prior tocompletion of the full opening stroke. If no reclosing power is beingapplied to the piston 15 when the latch becomes reset, the contactcontinues to move upwardly toward its fully open position.

That the mechanism is mechanically trip-free is demonstrated by the factthat during the above-described tripping operation of the breaker fromthe position of Fig. 2 toward the position of Fig. 3, the position ofthe piston at the upper end of the cylinder can remain unchanged. Thus,the breaker is capable of tripping free of the piston 15 even if closingpower is being applied to the lower side of piston 15 at the instant oftripping.

If it is unnecessary to provide for rapid reclosing duty, then closingpower may be applied to the piston 15 at any desired time aftercompletion of the above-described opening stroke. For example, toreclose the circuit breaker from the open position of Fig. 3, it isnecessary merely to drive the piston 15 downwardly as indicated by arrow60. This may be accomplished by supplying pressurized fluid throughconduit 45, as indicated by arrow 61. Since the latch member 35 is resetin the position of Fig. 3, the toggle support pin 25 is fixed and,accordingly, the primary toggle 20, 21 is capable of transmittingclosing thrust from piston 15 to the contact operating rod 13.Accordingly, downward movement of piston 15 extends the primary toggle20, 21 into the position of Fig. 4 thereby to move the operating rod 13toward contact-closed position. As the primary toggle moves into itsextended position of Fig. 4 its knee 22 first displaces and then movesunder the lower surface of prop member 50, where it is maintained by theprop against the bias of the opening spring 12. A prop biasing spring 52ur es the prop into a position to maintain the toggle extended so longas the latch member 35 is in its latched position.

It will be apparent from the above described cycle of operation, that ifthe circuit breaker is tripped after the driving piston 15 has moved thebreaker toward closed position, it is unnecessary to retract the pistonand repeat the upward piston closing stroke in order to again reclosethe breaker, as is necessary in the usual breaker. My invention makes itpossible to utilize the piston retracting movement to reclose thebreaker. No additional piston movement is required. For example, if thecircuit breaker is tripped into the position of Fig. 3 after the drivingpiston 15 has moved upwardly to drive the breaker from the open positionof Fig. 1 toward the closed position of Fig. 2, it is unnecessary tosubsequently lower the piston 15 prior to initiating a reclosingoperation. This reclosing may be carried out simply by driving thepiston downwardly from the elevated position (of Fig. 2) that it hasassumed in originally closing the breaker. No further movement of thepiston is required. This reversiblyacting, closing characteristic of thepiston and operating linkage is an important feature of the presentinvention which permits extremely rapid reclosing of the circuit breakerwhen it is used for automatic reclosing duty. This may be illustrated bythe following description of trip-free close-open operation followed bya rapid reclosing operation; this being a type of duty desired, orrequired, in certain circuit breaker applications. Assume that as thepiston moves upwardly to close the breaker (as from Fig. l to Fig. 2), afault is present on the line. As soon as the fault current flows betweencontacts 19 and 11, the fault sensitive latch member 35 immediatelytrips, thereby causing the primary toggle to collapse and becomeincapable of transmitting continued closing thrust to the contact 10.Since the toggle collapses upwardly as indicated by the dotted lines ofFig. 2, the driving piston 15 can remain in its upper position. But, ifrapid reclosing is desired, a downward reclosing force may be applied tothe piston even before the latch member 35 has reset into the solid-linelatched position of Fig. 3. As will be explained in greater detailhereinafter, this downward reclosing force is immediately transmitted tothe secondary toggle 30 and performs the very desirable function ofaccelerating the return of the secondary knee 34 to its latchedposition. Obviously, this acceleration shortens the time for latchresetting and permits reclosure to be initiated more rapidly. As pointedout previously, once the latch member 35 is reset, the toggle supportingpin 25 becomes a fixed reaction point and, as a result, the primarytoggle is again capable of transmitting closing force. Thus, at theinstant the latch resets into the position of Fig. 3, the togglesupporting pin 25 again becomes a fixed point in its alternate lowerposition and the driving piston which is then moving downwardly underreclosing power, instantaneously reverses the up ward collapsingdirection of movement of the tripped primary knee 22 and begins movingthe knee downward toward toggle center. This reversal of primary toggleknee 22 is immediately transmitted to the contact operating rod 13 andis effective to immediately initiate reversal, or reclosing, of thecontacts 10, 11.

It will be apparent from this description of a rapid close-open-reclosecycle that by utilizing the downward, or return, movement of the drivingpiston 15 to effect reclosing, after its first upward closing movement,several highly advantageous results are obtained. First, it isunnecessary to reset, or retract, the driving piston prior to initiationof a reclosing stroke, and, as a result, no time is consumed in pistonresetting. Second, the downward, or return, movement of the pistonactually accelerates latch resetting and, accordingly, shortens thedelay normally required to permit latch resetting.

An important feature of applicants linkage which contributes to theabove-described ability of the piston to close the breaker by moving ineither of two mutually reverse directions in that closing movement ofthe breaker is efiected by moving the primary toggle knee 22 towardtoggle center on one side of toggle center, whereas a subsequent openingof the breaker results in movement of the toggle knee 22 away fromcenter but on the other side of center. This may be illustrated bycomparing the position of the primary toggle knee 22 in the dotted lineclosing position of Fig. l with the position of the knee in the dottedline opening position of Fig. 2. In these dotted line positions, theprimary toggle knee 22 is on the opposite sides of toggle center. Sinceclosing of the breaker may be effected only by moving the knee towardtoggle center, it is apparent that movement of the knee into positionson opposite sides of toggle center in response to successive openingoperations permits the breaker to be reclosed successively by moving theknee in reverse direction toward toggle center. Accordingly, the pistonis capable of carrying out a closing and a subsequent reclosing actionsimply by moving through one stroke and then returning to its originalposition.

Another feature which contributes to the abiilty of the circuit breakerto rapidly reclose is that the latch means 3035, after having beentripped out of one latched position, resets to another latched positionbefore the full opening stroke is completed. As a result, the primarytoggle is rendered capable of transmitting a reclosing thrust to thecontacts prior to completion of full opening stroke. This characteristichas been illustrated by the legends applied to the positions of theoutput crank 23 in Fig. 3, which show that the latch may be reset beforecompletion of a full opening stroke. Since reclosing power from thedriving piston accelerates latch resetting, as described above, it willbe apparent that the point of latch resetting may be varied by varyingthe instant at which reclosing power is applied to piston 15.

The manner in which reclosing power from the driving piston acceleratesthe latch resetting process may be more specifically explained byconsidering the condition of primary toggle link 20 after the mechanismhas been tripped. For example, consider the condition of link 20 afterthe mechanism has been tripped from the solid line position of Fig. 2and at the instant it passes through the dotted line position of thissame figure. At this instant, the link 20 is floating with respect tolink 21 and, accordingly, is free to pivot counterclockwise at anydesired speed about the upwardly moving primary knee 22. Obviously,accelerating such counterclockwise movement of the link 20 willaccelerate the downward arcuate travel of toggle support pin 25 alongare 52 and accordingly will accelerate the latch resetting process.Since the piston 15 is coupled to link 2t) at a point 42 which is spacedfrom the toggle knee 22, it will be apparent that downward movement ofthe piston 15 acting through the movement arm between 42 and 22 willaccelerate the above-described downward arcuate movement of togglesupport pin 25 and, accordingly, will accelerate latch resetting.

Another feature which is apparent from the above description of aclose-open-reclose operation is that the piston 15, through linkage 40,41, remains coupled to the primary toggle 29, 21 at all times, evenduring a trip-free close-open operation. The pivotally-mountedconnecting link 41 permits independent movement of the primary toggle20, 21 with respect to the piston but positively transmits motion fromthe piston to the toggle for both directions of piston movement. Thus,the piston 15 is not required to move with the toggle 29, 21 duringtripping, but because of its permanently coupled relationship with thetoggle, is capable of applying a reclosing force to the toggle at anydesirable instant after circuit interruption, even while the breakerparts are still moving toward their fully-open position.

The schematic layout of Fig. illustrates a control system forautomatically producing rapid reclosing operation of the circuit breakerof Figs. 1-4. This layout of Fig. 5 has been shown in simplified form inorder to facilitate an understanding of the control system. In thisfigure, the circuit breaker is shown in closed position with the piston15 elevated and the latch means 34 35 in its upper latched position, inthe same manner as shown in Fig. 2. For initiating a tripping operationthere is provided a current transformer 70 and a relay '71 in circuittherewith. For illustrative purposes, the relay 71 is shown as anovercurrent relay having normally-open contacts 72, 73 which areclosab'le in response to overcurrent in power circuit 9, as sensed bycurrent transformer 70. Closing of the contacts of relay 71 establisheda tripping circuit across the opposed terminals 74 and 75 of a D. C.control power source. This tripping circuit includes the seriescombination of contacts 72, '73, conductor 76, tripping solenoid 38 andconductor 77. Thus, when contacts 72, 73 close in response toovercurrent in circuit 9, the tripping solenoid 33 will be energized .tounlatch latch member 35, thereby freeing the secondary toggle knee 34.so that the mechanism may be collapsed toward the dotted line positionshown in Fig. 2 by the then-freed contact opening spring 12. At someintermediate point prior to complete resetting of the latch means 39, 35into .its lower holding position shown in Fig. 3, the toggle support pin25 strikes a movable biasedopen auxiliary contact 78 (Fig. 5) which isdriven into extended wiping engagement with a cooperating fixed contact79; Immediately prior to this intermediate point, the auxiliary contacts80 on the then-opening circuit breaker operating rod 13 will have closedthereby closing a reclosing relay 31, which seals itself closed throughseal-in contacts 81a. Thus, it will be apparent that as soon as thelatch-controlled contacts 78 and 79 close, a reclosing circuit isestablished through the valve control coil 32a of a closing controlvalve 82. This reclosing circuit extends from supply line 74 through thethen-closed contacts 81b of relay 81, the contacts 831) of a lockoutdevice 83, conductor 84, the then-closed co.ntacts 78, 79, conductor 85,limit switch 86, conductor 85a, valve control coil 82a and then to theopposite supply line 75. The lockout device 83 is shown schematicallysince it maybe a conventional construction which locks out in responseto a predetermined number of closely-spaced circuit reclosures. Uponlockout, it functions to lock open its contacts 831) so as to preventmore than said predetermined number of closely-spaced circuitreclosures. Additionally, lockout of the device 83 opens the contacts83a to effect opening of the then sealed-in reclosing relay 81. Assumingnow that the contacts of the lockout device are closed, completion ofthe above reclosing circuit at contacts 7$, 79 immediately opens valve82 by moving its operator 87 into the dotted line position, therebypermitting pressurized fluid to flow from a reservoir (not shown),through header 87a, and then through valve 82 to the top side of thedriving piston 15 whereby to apply reclosing power to piston 15. It willbe apparent that by varying the point at which thelatch-controlled'switch 78, '79 closes, the instant at which reclosingpower is applied to piston 15 may be varied. If the piston 15 hasbegunits downward reclosing movement .at .the instant the latch means as, 35resets into its lower position (of Fig. 3), continued downward movementof the piston 15 will be effective to immediately return the contactoperating rod 13 toward its closed position of Fig. 4. When the pistonreaches a point adjacent its lower limit of movement it opens thepreviously-closed limit switch 36, thereby permitting valve 32, underthe bias of spring 88, to cut ofi fluid liow into the motor and to ventthe residual pressure in the motor through port 89, whereby to removeclosing power from the piston 15.

The operation of the system follows substantially the same pattern ifthe latch and piston occupy their respective lower positions at the timeof tripping. Under such conditions, the toggle support pin 25 would moveupwardly during the tripping-open operation to close the then-open upperauxiliary contacts 99, 91 (which correspond to the lower auxiliarycontacts 78, 79 thereby completing a second reclosing circuit throughthe thenclosed limit switch 92 and coil 93 of the lower closing controlvalve 94. Energization of coil 93 would raise the lower valve operator96 into the dotted line position whereby to supply pressurized reclosingfluid to the lower side of the then-lowered piston 15. This applicationof reclosing power would continue until the piston was elevated into itsupper position where it efiects opening of the limit switch 92, therebypermitting the valve 9- under the bias of spring 97 to cut off the flowof fluid into the cylinder and to vent through port 98.

It will be understood that any desired nurnber of .successive open-closeoperations may be performed by the trip-free mechanism of my invention.With the aid of a conventional timer (not shown) suitably connected inthe energizing circuit for the fault responsive relay 71, the timeinterval between these successive operations may advantageously be madeas short or as long as des red.

For manually initiating a closing operation, 1 have provided apush-button switch 9 which, when closed, establishes an energizingcircuit for the proper closing control valve 82 or 94.

It should be understood that my invention is not limited to the specificconstruction illustrated herein, and that changes and modifications mayoccur to one skilled in the art without departing from the spirit of myinvention. For example, although I have shown a fluid motor as thesource of motive power for closing the illustrated circuit breaker, itwill be apparent that any suitable source of motive power having adriving member capable or applying power in reverse direction may beused without departing from the present invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In combination, a switch member movable between open and closedpositions, collapsible toggle mechanism coupled to said switch memberand having a knee movable between positions on opposite sides of togglecenter, a source of motive power having a movable driving memberconnected to move said knee toward toggle center on one side of saidcenter thereby to move said means etfective in a pair of alternatelatched positions to maintain said toggle mechanism operative totransmit closing thrust to said switch member, said toggle mechanismhaving a knee movable in one direction to effect closing movement ofsaid switch member when said latch means is in one of its latchedpositions, said knee being movable in a generally opposite direction toeffect closing movement of said switch member when said latch means isin its other latched position, means responsive to tripping of saidlatch means out of one of its latched positions for moving said toggleknee relative to toggle center and in the same general direction as thedirection in which the knee was moved during the closing movement whichimmediately preceded tripping of said latch means whereby to effectopening movement of the switch member, a fluid motor having a pistonreversibly movable to reversibly drive said knee in either of saiddirections toward switch closed position, and a linkage coupling saidpiston to said toggle mechanism during movement of said piston andduring tripping of said trip-free latch means.

21. In combination, a switch member movable between 14 open and closedpositions, a thrust toggle linkage coupled to said member, means forapplying force in one direction for driving said toggle linkage to afirst generally dead-central position for closing said switch member,holding means for supporting one end of said toggle linkage during saidapplication of force and trippable to free said toggle linkage to permitsaid switch member to open, means for shifting said one end of saidtoggle linkage coincident with the tripping movement of said holdingmeans whereby to establish a second dead-central position for saidtoggle linkage, and means for applying an alternate closing force in adirection generally opposite to said one direction for driving saidtoggle linkage to said second central toggle position, whereby toreclose said switch member.

References Cited in the file of this patent UNITED STATES PATENTS

